On-off timer mechanism with individual setting counters



Aug. 23, 1966 F. SCHEMBERA 3,268,677

ON-OFF TIMER MECHANISM WITH INDIVIDUAL SETTING COUNTERS Filed July 5, 1965 2 Sheets-Sheet l INVENTOR.

Fmzomc H Sc/{EMBERH 3, 1966 F. SCHEMBERA 3,268,677

ON-OFF TIMER MECHANISM WITH INDIVIDUAL SETTING COUNTERS Filed J ly 5, 1963 2 Sheets-Sheet Fig. 2

INVENTOR. FRIEDRICH Sew/ 15mm JrToRN/r Ys United States Patent ()fi ice 3,258,677 Patented August 23, 1966 3,268,677 ON-OFF TIMER MECHANISM WITH INDI- VIDUAL SETTING COUNTERS Friedrich Schembera, Bretten, Baden, Germany, assignor to Neif-Werke Carl Nelf G.m.b.H., Bretten, Baden, Germany Filed July 5, 1963, Ser. No. 293,095 Claims priority, application Germany, July 11, 1962,

12 Claims. (Cl. ZOO-38) The present invention relates to an electric switch clock with a time-controlled drive mechanism.

The automatic operation of machines, heating or refrigerating apparatus, cooking and bakin-g stoves or ovens for industrial or household use, as well as of many other types of apparatus is usually effected by switch clocks which may be set at different degrees of accuracy to carry out one or more switch operations at preselected times.

Thus, for example, there are switch c-locks known in which a disk which revolves in a 24-hour cycle and is driven by a synchronous motor or a spring mechanism is provided with riders which may be set in accordance with the switching times selected, that is, the times at which the switch operations should occur. The manipulation for setting such switch clocks is very complicated and they are therefore usually employed only for carrying out control functions which remain daily the same for a longer period of time. Switch clocks for constantly changed switching times are used primarily for electric cooking stoves and are usually provided with a 12-hour graduation which is sufficient for this purpose. Such switch clocks are either equipped with an instrument dial on which the desired switching time may be set by hand or with a fixed dial and a manually adjustable knob or handle. When setting the dial or knob, a spring mechanism is tightened which then drives the switch clock in accordance with the actual time. These switch clocks are, however, able to effect only one switching operation, for example, to switch on the stove. More recently, such switch clocks are employed in pairs, one of which when in the zero position closes the circuit, while the other opens the circuit in the zero position. Both clocks are connected in series. By means of the first clock, the stove or other apparatus is switched on at the desired time, while the other clock switches it off at the desired time. For this particular purpose, such a clock arrangement has proved satisfactory, except for the degree of accuracy of the times of its switching operations.

In many cases it is, however, required that the switch clock will operate exactly to the minute even after a relatively long waiting period. When employing conventional switch clock mechanisms this would mean that they would have to be extremely accurate and therefore so expensive that their cost would not be in a proper proportion to the cost of the appliance which they should control. Furthermore, due to their construction the mentioned switch clocks have the disadvantage that it is not even possible to set the switching times accurately since the time dials have to be made of a relatively small diameter so as to be in proportion to the size of the appliance. Deviations of to minutes are therefore practically unavoidable. Such deviations may, however, be extremely disagreeable or even dangerous, especially if they sum up. Thus, for example, in a st-ove or oven, the food may be ruined by being cooked or baked too long or not long enough, and deviations of as much as 20 minutes may spoil it completely.

It is the principal object of the invention to provide an electric switch clock with a time-controlled drive mechanism which overcomes the above-mentioned disadvantages, may be produced at a relatively low cost, and permits the switching functions to be carried out at very accurate times and, if required, even to a fraction of a second.

According to the invention, this object is attained by providing the switch clock with at least one digital computing c-ounter which is driven at a speed in positive relation to the actual clock time and is adapted to effect one switch operation, further with a differential gear preceding and connected to the computing counter for producing a reverse rotation of this counter in proportion to the period of time, hereafter called the waiting period, which intervenes between the time at which the counter is set and the time of the switch operation, and with means actuated by the computing counter for effecting the switch operation.

The present invention therefore provides a separate computing counter for each different switch operation. These computing counters together with their differential gears and a time counter which is driven directly and indicates the actual clock time may be mounted on a common shaft which is preferably driven by a self-starting synchronous motor through a speed-reduction gear and a slip clutch. Each of the differential gears preferably comprises a pair of coaxial bevel gears, a spur gear which revolves freely between these bevel gears, and a satellite which is radially mounted in the spur gear and is in engagement with the two bevel gears. Each of the computing counters is associated with a further counter, a settin-g counter, on which the desired switching time may be set by hand and which is preferably designed in the same manner as the time counter. For entering rotary motions which correspond to the waiting period int-o the differential gear and thus into the associated computing counter, each of the shafts driving the setting counters may be provided with a spur gear which is in engagement with the spur gear of the associated differential gear and has the same number of teeth as the latter. The computing as well as the setting and time counters may be of a conventional type in the form of roll counters, each of which comprises three rolls which are respectively designed for the minutes from O to 9, the full decades from 0 to 5, and the hours from 1 to 12. The rolls at least of the time and setting counters are also marked accordingly. The first roll of each counter preferably advances continuously, while the subsequent rolls advance by jumping from one digit to the next. The advance of each second and third roll from one digit to another is produced by sprockets which are rotatably mounted between the counter rolls on a shaft which extends parallel to the shaft of these rolls.

It is of course also possible to design the switch clock according to the invention so that its 12-hour graduation is extended to a 24-hour graduation. This would only require the third roller of each counter to be designed for the hours from 0 to 23 and also the third roller at least of the time and setting counters to be marked accordingly.

It also lies within the concept of the invention to provide at least the time and setting counters for special purposes with figures for indicating the months of a year. For this purpose each counter is preferably provided with additional fourth and fifth rolls, the fourth being provided with the numerals from 0 to 9 and the fifth with the numerals from 0 to 3. The third roller of each counter is then again provided with the numerals from 0 to 23 for a 24-hour graduation. Since the graduation in months deviates from the graduation of the counters, the application of such a switch clock is limited, however, insofar as for carrying out a switch operation on a certain date of the next month, the switch clock must be accordingly adjusted by turning back the computing counters and the time counter.

The switch clock may be further provided with indications of the days of the week. For this purpose, the third roll of each counter may be provided with numerals from to 23 in accordance with a 24-hour graduation, and each counter should be provided with anadditional roll which is graduated and may be marked in accordance with the seven days of the week.

In a similar manner it is possible to design the switch clock for other time graduations by providing the counters with additional rolls which are graduated and may be marked in accordance with different time graduations, for example, the months, weeks, and days of a year. Also, a continuous indication of the seconds, minutes, and hours may be provided so that the switch clock according to the invention will switch on a certain apparatus after the expiration of, for example, exactly 2,748,077 seconds from a certain time, that is, after 763 hours, 21 minutes, and 17 seconds, and will then switch it off after seconds.

For indicating the clock time and for setting the switching time, the rolls of the setting and time counters may, for example, be provided on their peripheral surfaces with a uniformly graduated numbering in accordance with their specific purposes. For effecting the switch operations each roll of the computing counters may be provided with an arcuate recess in its peripheral surface. When the preset switching time coincides with the actual clock time, these recesses in all rolls of the respective computing counter will be in alignment with each other. In order to prevent the differential gear of each computing counter from being acted upon by an additive rotation, the drive shaft of each setting counter is provided with one-way locking means which preferably consists of a ratchet and a resilient pawl.

The setting counters may be set to the desired switching times by manually driven transmission means, for example, by an intermediate gear with different gear ratios which may be employed selectively. This intermediate gear is preferably driven by two coaxial shafts which for a simple manipulation are also provided with coaxial rotary control knobs. By this setting device it is possible first to carry out the coarse adjustment of the setting counters very quickly at high gear ratio and then the fine adjustment at a lower gear ratio. Since the setting counters are to be alternately driven by the same intermediate gear, the parts of their shaft connections between this gear and the one-way locking means are provided with slip clutches so that, when one shaft is rotated while the other is locked by the one-way locking means, i.e., the pawl and ratchet, the slip clutch of the second shaft will be disengaged and this shaft will thus not be driven by the intermediate gear.

Even though the switch clock according to the invention is driven by a synchronous motor, it may occur that the clock has to be reset, for example, after the current supply has been interrupted. The switch clock is for this purpose provided with a setting device Which consists of a rotary control knob which when turned acts through a set of bevel gears directly upon the shaft which is driven by the synchronous motor.

The switch mechanism of the switch clock preferably comprises two sets of three small control rollers. Each set of these rollers is mounted on a separate shaft and engages with the peripheral surfaces of the rolls of the respective computing counter and is adapted to engage simultaneously into the arcuate recesses thereof. These rollers are preferably made of a diameter in accordance with the size of the arcuate recesses in the computer rolls. The shafts carrying these rollers may, for example, be connected to compound lever transmissions, the driven ends of which are adapted to engage with cams which are preferably mounted on a plate which is movable under the action of a spring in the direction of its plane toward the ends of the levers, and which are staggered on the plate at different levels in the direction of movement of the plate. When the control rollers engage into the arcuate recesses of the computing rolls, the cams on the plate are disengaged from the ends of the levers and the plate advances by the distance of one cam. Preferably on the side opposite to that carrying the mentioned cams the plate is further provided with control cams upon which the end of the actuating lever of an electric switch engages. The movements which are produced by the computing counters thus effect either the closing or opening of an electric circuit.

In order to permit the automatically controlled elements of the switch clock also to be set by hand, the clock is further provided with suitable devices by means of which it is possible to interrupt temporarily only certain automatic control functions of the mechanism or the entire automatic operation thereof.

If the switch clock is designed for operating within large periods of time, the invention further provides an electric setting motor which preferably replaces the intermediate gear for the coarse and fine adjustment of the setting counters. This motor may be provided with suitable conventional means for reversing its direction of rotation and also for varying its speed. In order to permit the fine adjustment to be made by hand, the setting motor may be provided with a drive shaft which may be extended at one end on which a knurled control knob may be mounted.

The above-mentioned as well as further features and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying drawings, in which- FIGURE 1 shows, partly in cross section, a plan view of the switch clock according to the invention; while FIGURE 2 shows a perspective view of the switch mechanism of the switch clock.

The switch clock according to the invention essentially consists of a combination of five roll counters A, B, C, -D and E of a conventional type with a switch mechanism F. Counter A indicates the actual clock time and serves as a time counter, counters B and C are the computing counters, and counters D and E are setting counters on which the times of the different operations of the switch are set. Each counter consists of three rolls 1, 2, and 3a to e, respectively, which are combined into a group and are provided with the requisite number of teeth, and two sprockets 4 and 5a to e, respectively, for the sudden advance of the subsequent rolls 2 and 3a to e, respectively. The three groups of rolls 1, 2, and 3a to c, respectively, of the time and computing counters A, B, and C are mounted on a common shaft 8 which is driven by a synchronous motor 6 through a speed-reduction gear and a slip clutch 7, while each group of rolls 1d, 2d, 3d and 1e, 2e, 3c, of the setting counters D and E, respectively, is mounted on a shaft 8:1 or 8e, respectively, which extends parallel to shaft 8. Parallel to each of the shafts 8, 8d, and 8e a further shaft 9, 9d, and 9e is provided on which the respective sprockets 4 and 5 which are associated with each group of counter rolls are rotatably mounted. The adjacent counters A and B, on the one hand, and B and C, on the other hand, are separated by differential gearing, each of which consists of a bevel gear 10b or 10c which is rigidly secured to shaft 8, a spur gear 1112 or Me which is freely rotatable on shaft 8, a second bevel gear 13b or 130 which is also freely rotatable on shaft 8, and a satellite 12b or which is radially mounted in the spur gear 11b or .1- 1e and in engagement with the two bevel gears of the particular differential gearing. The bevel gears 13b and which are freely rotatable on shaft 8 are rigidly connected to the first rolls 1b and 1c of the computing counters B and C, respectively; A further bevel gear 14a is rigidly secured toshaft 8 and likewise rigidly connected to the first roll 1a of the time counter A. This bevel gear 14a engages with another bevel gear 16 which is connected to a setting knob 15.

On one end of shaft 8d a spur gear 17d is mounted which engages with and has the same number of teeth as the spur gearing 11b of the differential gear which is interposed between the counters A and B. The same applies to a spur gear 17s on shaft 8e which engages with the spur gear 110 of the differential gearing between the computing counters B and C. For a better illustration, this gear connection is shown in an exploded view in FIGURE 1.

Shafts 8d and 8e are driven at their other ends by a pair of bevel gears 18d or 18e, respectively. Each shaft 8d and 8e further has a one-Way ratchet gear 19d or 19e rigidly secured thereto, each of which in connection with a resilient pawl 20 or 20e insures that each setting counter D and E can only be driven in one direction. Each of the coaxial shafts 22d and 22:: is provided with a slip clutch 21d or 22e and connected at one end to the bevel gears 18d or 1'8e, respectively, and carries at the other end a gear 23d or 23e, respectively. Gears 23d and 232 are exactly equal and both engage with the larger gear rim of a step wheel 24 which is rigidly secured to a further shaft 26 which carries a rotary control knob 25. Step wheel 24 forms a part of an intermediate gear 27 which is driven by a hollow shaft 29 which contains the shaft 26 and is provided with a cup-shaped rotary control knob 28 which loosely surrounds the rotary control knob 25.

The peripheral surfaces of the counter rolls 1, 2, and 3a, d, and e of the time and setting counters A, D, and B, respectively, are provided with equal sets of numbers, that is, with the numbers from O to 9 on the first rolls In, 1d, and la, the numbers from to on the second rolls 2a, 2d, and 2e, and the numbers from 1 to 12 on the third rolls 3a, 3d, and 3e. For effecting the switching operation, the peripheral surface of each roll 1, 2, and 3b and 0, respectively, of the computing counters B and C is provided with an arcuate recess 31, 32, or 33b or 0, respectively, as indicated in FIGURE 2 in dotted lines.

Into these recesses 31, 3'2, and 33b or c, respectively, smaller rollers 1f or 2 are adapted to engage which are mounted on a shaft 3 or 4], respectively. These shafts 3] and 4 are rigidly connected at right angles to a pair of equally directed arms of two equal angular levers 5i and 6 which are separately pivotable on a shaft 7 Parallel to and at the same level as shaft 7 a further shaft 8 is provided on which two further angular levers 9] and 10 are mounted the arms of each of which extend at a slightly obtuse angle to each other. The shafts 7) and 8 are rigid and may be fastened to the walls of the switch housing (not shown). The shafts 3f and 4f are supported freely for bodily movements by the levers 5f, 6 but their free ends can be guided each within a suitable slot (not shown) in the aforesaid walls of the switch housing. The angularly related arms of the levers 5f, 6 and also the similarly disposed arms of the levers 9 and 10 are, in the case of each pair of angularly related arms, rigidly connected to each other so that each of the levers 5f, 6 9 and 10 forms a bell crank. The bell cranks constituted by levers 5 and 6 are connected at one end of one of the arms of each lever to one end of a respective arm of levers 9f and 10 by pin-and-slot joints. These .are urged by springs 11 and 12 in a direction causing the ends of the levers remote from the joints to tend to pivot toward each other, such pivoting motion actually occurring upon the expiration of the waiting period preceding the closing of switch 207 as explained in detail hereinafter so that the corresponding leevrs 5 6f and 9f, 10 tend to pivot toward each other. The free arms of levers 97 and 10 extend horizontally in the direction opposite to that in which they tend to move. Shaft 8 has a further lever 13f pivotable thereon which is bent at the same angle as levers 9f and 10f and is acted upon by a spring. In front of the free arms of levers 9f, 10 and 13 a plate 14 is mounted in a vertical position and provided with cam projections 15 16 and 17 which serve as stops and extend in the direction toward the levers 9f, 10], and 13 respectively. The opposite side of plate 14 carries two control cams 18f which are separated by a recess of substantially the same size as these cams and are adapted to engage with the end of the actuating lever 19 of an electric switch 20 The cam projections 15 16 and 17 are disposed at different levels, being staggered relative to each other by one half of the distance between the centers of the two control cams 18f. A compression spring 21f presses the plate 14 upwardly and the cams 15 16 and 17] thereon toward the free ends of levers 9f, 10 and 13 respectively. The upper edge of plate 14 carries a push-button 22 A further pushbutton 23 is pivotably connected to the lever 24 which is pivotable about shaft 8 Vertically to its plane of rotation, this lever 24 carries a rod 25 for manually releasing the levers 9f, 10 and 13f.

The operation of the switch clock according to the invention will now be described in the form of an example.

The synchronous motor 6 drives the shaft 8 through a reduction gear at a speed of 6 rpm. The counter roll 1a of the time-indicating counter A which is secured to shaft 8 therefore indicates through a Window, not

shown, the minutes as they pass continuously from 0 to 9. After each revolution of roll 1a, the sprocket 4a suddenly advances the next counter roll 2a by one digit which corresponds to one full decade. The same procedure is repeated after each revolution of roll 2a with a corresponding action upon the third counter roll 3a which indicates the full hours. At the same time, a rotary component which is equal to the speed of shaft 8 is entered into the differential gears through the bevel gears 10b and 10c which are secured to shaft 8. When the setting counters D and E which may be set to the switch-operating times are not in operation, the spur gears 11b and of the differential gears are also stopped so that the computing counters B and C are driven merely by the coaxial bevel gears. The direction of rotation of these computing counters B and C is then opposite to that of shaft 8. Counter rolls 1, 2, and 3b and c of the computing counters B and C, respectively, are then advanced in the same manner as the rolls 1, 2, and 3a of the time counter A.

It is assumed that at the time of observation the setting counters D and E on which the switch-operating times may be set indicate a group of numbers which does not correspond with the actual time. Consequently, the arcuate recesses 31, 32, and 33 which are provided in the rolls 1, 2, and 3b and 0, respectively, of the computing counters B and C are not in alignment with each other and therefore the rollers 17 and 2) cannot engage therein. It is further assumed that the actual time is 2:45 oclock and that the mechanism is to be set so that the switch 20 will be closed at 5:10 oclock and opened at 6:20 oclock.

For this purpose it is necessary to operate the outer control knob 28 to effect through the intermediate gear 27 the coarse adjustment of the setting counters D and E and then to operate the central knob 25 to effect the fine adjustment of these counters. According to the invention, the setting counters D and E are set separately and subsequently to each other by turning each of the knobs 25 and 28 first in one and the-n in the opposite directions. The two shafts 8d and 8e are then turned in equal directions. These separate adjustments are possible because of the particular arrangement of the bevel gears 18d and 18s and their cooperation with the slip clutches 21d and 21c and the pawl and ratchet means 19d, 19c, 20d, and 202. When the knobs 25 and 28 are turned in the direction in which the setting counter D is to be rotated, this would mean that shaft 8e would be rotated in a direction which is contrary to the proper direction of rotation of the setting counter E. This irnproper rotation of shaft 8e is prevented by the one-way ratchet 1% and the resilient pawl 20c, whereby shaft 21s is disengaged.

The rotation of the setting counter D until the switchclosing time of :10 oclock is set is entered into the differential gearing which precedes the counter B as a second rotary component which is negative to the positive rotary component from the shaft 8. If at the beginning of the adjustment the setting counter D indicates a time which is earlier than the actual time, rolls 1, 2, and 3b of the computing counter B then pass beyond the position at which the recesses 31, 32, and 3312 are in alignment with each other. This occurs at the moment when the time indicated by the setting counter D coincides with the actual time. The further rotation of the setting counter D up to the desired switch-closing time corresponds to the waiting time and is compensated during this period by the rotary component coming from shaft 8 which is entered into the differential gearing so that at the expiration of this time, the actual clock time and the time of the setting counter D again coincide with each other. The same procedure is repeated as regards the setting counter E, but because of the provision of the bevel gears 18d and 18:: it occurs in the opposite direction of rotation of the control knobs 25 and 28.

During the adjustment of the switch clock, plate 14 is located either at a level in which the stop projection 17 is in engagement with the lever 13 or it is located in its upper end position after the release button 23 is depressed. in both cases, the procedures occurring during the setting operation remain without effect upon the operation of the switch clock. When the adjustment is completed, p u'shbutton 22 is depressed to move to its lowest position, whereby because of the wedge-shaped form of the cam projections 15 and 16f, the free ends of the levers 5 6 9], and 107 are pushed aside. The actuating lever 19 of switch 20 is thereby pushed by the upper control cam 18 to the off position.

After the waiting period preceding the switch-closing time, that is, at 5:10 oclock, has expired, rolls 1b, 2b, and 3b of the computing counter B have reached the position in which their recesses 31b, 32b, and 33b are in alignment with each other so that the rollers 11 can engage therein. Due to the tension of spring 11 the two angular levers 5 and 9f pivot toward each other. The end of lever 9 which until this time was in engagement with cam 15] thereby releases this cam, and plate 14f is then moved by the compression spring 21] until cam 16f engages with the end of the lever At the same time, the actuating lever 19f slides between the two control cams 18 and turns on the switch 20 so that the electric current can then flow in the circuit.

As long as plate 14f is held arrested by the cam 151 and the lever 91'' which is connected to the switchclosing setting counter B, the operations of lever 10 which are caused by the computing counter C remain without effect. The waiting period of counter B may therefore amount up to 12 hours and the point of time when the switch is to be opened may be set so as to occur at any desired time thereafter.

The above-mentioned procedures recur when the waiting period preceding the switch-opening time expires, that is, at 6:20 oclock. Plate 14 is then again advanced by the compression spring 21 by the distance between two cam projections so that the lower control cam 18 turns off the switch. Cam 17 is then in engagement with the end of lever 13 and is held arrested in this position. This completes the entire operation of the switch clock and an undesired repetition thereof is impossible.

. If the apparatus which is controlled by the switch clock is to be switched on and off by hand without any opera- 8 tion of the switch clock, switch 20 must remain continuously closed. This is effected by depressing the release button 23 Lever 24] is hereby pivoted so thatthe rod 25f pushes the lever 19f in the counterclockwise direction and thereby dis-connects the latter from cam 17f on plate 14 Plate 14 is then pushed upwardly by the spring 21 until it is in its upper end position. The switch lever 19f is then located underneath the two control cams 18 so that switch 20 closes the electric circuit.

Since rod 25 on lever 24] is also movable along the levers 9 and 10 it is possible at any time after the switch clock has been set and started to interrupt its operation by depressing the release button 23 Although my invention has been illustrated and described with reference to the preferred embodiment thereof, I wish to have it understood that it is in no way limited to the details of such embodiment, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed by invention, what I claim is:

1. An electric switch clock comprising time control driving means, a switch, at least one digital computing counter driven at a speed in a positive relation to the actual time and adapted to effect one switch operation, at least one differential gearing comprising a gear member operatively connected to said driving means and further comprising a further gear member, said differential gearing preceding and being connected to said computing counter for producing a reverse rotation of said counter in proportion to a waiting period intervening between the time at which said counter is set and the time of the desired switch operation, at least one setting counter associated with said digital computing counter, means actuated by said computing counter for effecting the switch operation, said switch clock further comprising a plurality of said computing counters for effecting several switch operations and each of said computing counters being preceded by a separate differential gearing, each said differential gearing comprising a pair of coaxial bevel gears, a spur gear, and a satellite mounted radially within said spur gear and in engagement with said bevel gears, and a time counter directly driven by said driving means for indicating the actual time, a common shaft carrying said computing counters, said differential gears, and said time counter, said driving means comprising a self-starting synchronous motor connected to said shaft and speed reducing means. and a slip clutch interposed between said motor and said shaft.

2. An electric switch clock as defined in claim 1, further comprising a plurality of setting counters each operatively connected with one of said computing counters and adapted to be set by hand to the desired switching time and each having a shaft and a spur gear on said shaft in engagement with and having the same number of teeth as said spur gearing of the associated differential gear and adapted to enter in said differential gearing the rotation corresponding to said waiting period.

3. An electric switch clock as defined in claim 2, in which all of said computing counters, setting counters and time counter are similar, each having three counter rolls graduated respectively according to minutes from'O to 9, to full decades from 0 to 5, and to hours from 1 to 12, and two rolls having operating connections with said three counter rolls effective for suddenly advancing the second and third counter rolls from one digit to another.

4. An electric switch clock as defined in claim 3, in which the peripheral surfaces at least of the rolls of said setting and time counters have indications in accordance with their graduations, and the peripheral surfaces of the rolls of said computing counters have arcuate recesses therein, said recesses of the rolls of each computing ounter being in alignment with each other when the switchoperating time as set on the respective setting counter coincides with the actual time.

5. An electric switch clock as defined in claim 2,

further comprising common setting means and separate connecting means connecting said setting means to respective ones of said shafts of said setting counters, and locking means for locking said shaft of one of said setting counters when the other setting counter is being set by said setting means.

. 6. An electric switch clock as defined in claim 5, in which said setting means comprise a pair of setting shafts, control knobs connected to said setting shafts for rotating the same, and transmitting means for transmitting the rotation of said setting shafts at different speed ratios to said shafts of said setting counters for a coarse and fine adjustment of said setting counters.

7. An electric switch clock as defined in claim 5, each said separate connecting means comprising clutch means for disconnecting said common setting means from one of said shafts while said shaft is locked and the other shaft is rotated and the setting counter thereon is being set by said common setting means.

8. An electric switch clock as defined in claim 1, further comprising means for rotating said shaft independently of said motor for adjusting said time counter to the actual time.

9. An electric switch clock as defined in claim 4, further comprising a shaft, a plurality of small rollers rotatably mounted on said shaft and engaging with the peripheral surfaces of the rolls of one of said computing counters and all adapted to engage into said arcuate recesses of said rolls when said recesses are in alignment with each other.

10. An electric switch clock as defined in claim 9,

further comprising compound levers each carrying at one end one of said shafts with said rollers thereon, a control element,cam members mounted on and projecting from said control element in the direction toward said levers and staggered at difierent levels relative to each other and each adapted to engage with the other end of one of said levers, spring means acting upon said control element to move said element in the direction toward said other ends of said levers so as to move one of said cam members into engagement with the other end of one of said levers, each of said levers being disengaged from its associated cam member when said rollers engage into said arcuate recesses in said rolls of the associated computer counter.

11. An electric switch clock as defined in claim 10, further comprising control cams on said control element adapted to engage with said switch for actuating the same when said control element is moved to different positions.

12. An electric switch clock as defined in claim 1, further comprising manually controlled means for interrupting the action of at least one of said computing counters upon said switch.

References Cited by the Examiner UNITED STATES PATENTS 2,557,464 6/1951 Rambert 235-l32 2,605,833 8/1952 Bliss 200-39 3,005,062 10/1961 Zagorski 200- X 3,028,083 4/1962 Beer 235132 X BERNARD A. GILHEANY, Primary Examiner.

H. M. FLECK, Assistant Examiner. 

1. AN ELECTRIC SWITCH CLOCK COMPRISING TIME CONTROL DRIVING MEANS, A SWITCH, AT LEAST ONE DIGITAL COMPUTING COUNTER DRIVEN AT A SPEED IN A POSITIVE RELATION TO THE ACTUAL TIME AND ADAPTED TO EFFECT ONE SWITCH OPERATION, AT LEAST ONE DIFFERENTIAL GEARING COMPRISING A GEAR MEMBER OPERATIVELY CONNECTED TO SAID DRIVING MEANS AND FURTHER COMPRISING A FURTHER GEAR MEMBER, SAID DIFFERENTIAL GEARING PRECEDING AND BEING CONNECTED TO SAID COMPUTING COUNTER FOR PRODUCING A REVERSE ROTATION OF SAID COUNTER IN PROPORTION TO A WAITING PERIOD INTERVENING BETWEEN THE TIME AT WHICH SAID COUNTER IS SET AND THE TIME OF THE DESIRED SWITCH OPERATION, AT LEAST ONE SETTING COUNTER ASSOCIATED WITH SAID DIGITAL COMPUTING COUNTER, MEANS ACTUATED BY SAID COMPUTING COUNTER FOR EFFECTING THE SWITCH OPERATION, SAID SWITCH CLOCK FURTHER COMPRISING A PLURALITY OF SAID COMPUTING COUNTERS FOR EFFECTING SEVERAL SWITCH OPERATIONS AND EACH OF SAID COMPUTING COUNTERS BEING PRECEDED BY A SEPARATE DIFFERENTIAL GEARING, EACH SAID DIFFERENTIAL GEARING COMPRISING A PAIR OF COAXIAL BEVEL GEARS, A SPUR GEAR, AND A SATELLITE MOUNTED RADIALLY WITHIN SAID SPUR GEAR AND IN ENGAGEMENT WITH SAID BEVEL GEARS, AND A TIME COUNTER DIRECTLY DRIVEN BY SAID DRIVING MEANS FOR INDICATING THE ACTUAL TIME, A COMMON SHAFT CARRYING SAID COMPUTING COUNTERS, SAID DIFFERENTIAL GEARS, AND SAID TIME COUNTER, SAID DRIVING MEANS COMPRISING A SELF-STARTING SYNCHRONOUS MOTOR CONNECTED TO SAID SHAFT AND SPEED REDUCING MEANS AND A CLIP CLUTCH INTERPOSED BETWEEN SAID MOTOR AND SAID SHAFT. 